Thermostatically controlled electric iron



Sept. 22, i942. w, A. BARNES 292959591 THERMOSTATICALLY CONTROLLED ELECTRIC IRON Original Filed Jan. 5l, 1958 Patented sept. 22, 1942 UNITED lSTATES PATENT OFFICE THERMOSTATICALLY CONTROLLED ELECTRIC IRUN William A. Barnes, Evansville, Ind., assignor to Dominion Electrical Manufacturing, Inc.

Original application January 31, 1938, Serial No. 187,883. Divided and this application July 19, 1940, Serial No. 346,430

7 Claims.

This applicationis a division of my application Serial No. 187,883, filed January 31, 1938, for

'Temperature responsive device.

plate of the iron to minimize the differential between the high and low peak of the ironing temperature.

Another object of my invention is the method of automatically supplying heat to an electric iron, in which the maximum and minimum temperatures of 'the-ironing surface are governed in accordance with a temperature gradient less than that of the entire base plate o f the iron.

A further object of my invention is to provide with the demand of the bottom of the base plate.

Still another object of my.inven`tion is to pro- A vide an electric iron having a thick base plate which comprises a reservoir for supplying heat to the bottom of the iron and which has a thermostat comprising metallic elements of ldiierent coeilicient of expansions with their ends joined, mounted with freedom oi movement throughout its entire length in a depression in the base plate for regulating-the supply of heat to the reservoir substantially in accordance with the demand of the bottom of the iron.

A further object of my invention is to prevent wide variations in the temperature of the'bottom of aniron by providing a heat reservoir for supplying heat to the bottom ofthe iron and by regulating the flow of heat to the reservoir in accordance with relatively small variations in the temperature of the bottom of the iron.

Other objects and a lfuller understanding of my invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawing, in which like parts are'designated by like reference characters, and in which:

Figure 1 shows a longitudinal cross-sectional 9 View of an electric iron employing my temperature device mounted in a depressed portion of the base plate ofthe iron; Figure 2 shows a transverse cross-'sectional view of my iron, taken along the line 2*-2 of Figure 1;

Figure 3 shows a graph representing the high and low peak of the ironing temperature of an iron, in which the differential between the high and low temperature peaks are relatively wide;

and

Figure 4 is a-graph similarI to Figure 3, in which the differential between the high and low peaks ofthe ironing temperature is reduced to a low minimum.'

In Figures l and 2, I show aptemperature responsive device 20 mounted in an electric iron having a base plate 18 and a4 shell 18. An extended heating element 88 is positioned on top of the base plate 18 and is held in position by means of a clamping plate 8|. The adjustment of the temperature responsive device may be effected by a temperature knob 83. As illustrated, the base plate 18 is relatively thick and possesses a relatively' high thermal capacity constituting a heat storage element. The central longitudinal portion of the base plate 18 is provided with a depressed portion 84 into which my temperature responsive device 20 may be inserted. The portion 85 between the bottom of the depressed portion 84 and the bottom of the base plate 18 is relatively thin, so thatv my temperature responsive device is substantially directly responsive to .the temperature of the material being ironed. The extended heating element 80.is in direct heat transfer engagement with the top of the base plate 16 and the heating capacity of the heating element is greater than any possible working absorption of heat from the iron in use. The temperature vresponsive device 20 is the saine as that shown and described in my application entitled Temperature responsive device led on- January 3l, 1938,` and assigned Serial No.

187,883, and from which this application was di..

high coeflicient of expansion and the longitudi- Y nal crimped strip-4 6 is preferably constructed of a piece of stainless steell which has a relatively low coeilicienti of expansion. 'As illustrated, the

central portion of the longitudinal crimped 'strip 46 is provided with an insulated actuating mem- I position by bolts 6i and t2.

ber 56 arranged to actuate a contact member d8 relative toa contact member di. member d8 is carried on the left hand end of a resilient contact nger i and the contact member dl is carried on the left hand end of a resilient contact'y finger 5t. The right hand ends of the resilientcontact fingers iii and 53 are positioned within the channel member l5 and are mounted to a supporting plate di) by means of insulating ,washers 59 and @il which are held in The contact The contact member lli is arranged to'be adjustably positioned with reference to the contact member it by means of an adjustable screw 'il threadably mounted through the clamping plate tli. is recessed and provided with an insulating member 'iiwhich directly engages the resilient con- The lower end of the adjustment screw lli tact linger 5t. The adjustment screw 'il may be y adjustably tur'ned'in any suitable manner. and as illustrated l employ the'lrnob @3 which may be actuated bythe user to regulate the temperature of the iron.v

The energization of the heating element dii is controlled bythe contacts [il and it governed by the contraction and expansion of the channel member d5 and the stainless steel strip (it.

When the temperature of the bottom portion of the base plate 18 .exceeds a predetermined value, as determinedby the settingoi the adjustment screw il, the aluminum channel member 35 expands and draws the central portion of the stainless steel strip d6 downwardly-and thereby permits the contact@ to separate irom the contact di to de-energize the heating element till. When the temperature of the bottom portion of the base plate 'i8 recedes to a predetermined low aeeaeoi dierentiai designates the temperature characteristic while ironing damp material and the peak periods having 'the -'smaller temperature diderential designates the 'temperature characteristic during idling. However, by employing a base plate ofrelatively high thermal capacity, the dierentialbetween the high and low peaks of the ironing temperatures is reduced or stabilized because the capacity ci the thick -base plate smcoths out the diierence between the' high and low temperatures.

Imy embodiment, l obtain the quick responsive- In order words, in

nessof a thin base plate and the smoothness yof a thick base plate, as shown in Figures'.

Although li have described my invention with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit andthe scope of the invention as hereinafter claimed. I claim as my invention: 1. An automatic electric irn having a base plate of relatively high thermal capacity constituting a heat storage element, said basefplate having a depressed portion therein, the thickness between the bottom o' the depressed portion value, the aluminum channel member i5 contracts and forces the central portion of the stainless steel .strip upwardly and causes the contact llt to engage the contact fill which closes the circuit for energizing the heating element dit.'

When the circuit is closed, the ow of the current may be traced from one terminal through a conductor 23, theheating elementv dii, a conductor 2t, the resilient contact finger 5i, the contacts d8 and `(di, the resilient nger ed, and a conductor 2li tothe other terminal. I

The vsupporting-plate i9 which is secured to the upper edges of they sides of. the channel d5 provides a shield or screen so that the heat from the heating element does not directly eect my responsive device 2B.l By mounting my temperature responsive device 2i) inthe bottom of the depressed portion 8f3, I-thereby provide for controlling the; energization of the heating element determined minini'uplftemperature, my temperature responsivefdevice restores the application of heat in` accordance .with a temperature gradientless fthagthatof' the entire base plate. If theentire' base plate were'as thin as the'v portion 85;; thediierental between the high and low peaks `offthe ironing temperature would .be quite large-,V as illustrated in Figure 3, in which the peak p'friods having the larger temperature',

' element beinggreater and the bottom of the base plate beingrelatively small, a temperature responsive devicecomprising metallic elements having different coecients of expansion mounted in the depressed portion, the element having the higher coei'icient or" expension rigidly engaging the bottom of the depressed portion and being directly responsive to the temperature of the thin portion of the base plate between thebottom of the depressed portion and the bottom of the base plate, an extended electric heating element in direct heattransferring engagement with the base plate, means for screening the heat responsive device from direct heating eiect of the heating element, the heat capacity of said element being `greater than any possible working absorption lof the ironing temperature.

A2. An' automatic electric iron having, abase plate oi' relatively highthermal capacity constituting a heat storageelement, said base. plate` having 'a depressed portion thereinthethickness between the bottom of the depressed portion and the bottom of they base plate being relatively small, a temperature responsive device comprising metallic velements l having diierent, coemcients of expansion mounted in thadepress'ed portion, ithe element havingvthe higherlcoe'i.- cient of expansion at all times rigidly engaging the bottom and sides of the depressed portion-i and being directly responsive to the temperature of the thin portion ofthe base'plate between'the bottom of the depressed portion andv the bottom. I

of the base plate, an extended velectric-cheating element in direct *heat-transferring engagement.. "'f'" with the base plate; means for screening; the heat'" i responsive device; from direct heating eiiecthot the heat capacity ofsai'd'" than any 'possible working# the iron vin use; and"""" 1` means forcausingthe temperature responsive 'J device to control the energizationV of the heatthe ,heating element,

absorption of heat from ing element in accordance with a temperature gradient less than that of the entire base plate to minimize the diierential between the high and low peaks of the ironing temperature.

3. An automatic electric iron having a base plate of relatively high4 thermal capacity constituting a, heat storage element, said base plate having a depressed portion therein, the thickness between the bottom of the depressed portion and theI bottom of the base plate being relatively small, a temperature responsive device comprising metallic elements having different coeilicients of expansion mounted in the depressed portion, the element having the higher coemcient of expansion at all times rigidly engaging the bottom of the depressed portion and being directly responsive to the temperature of the thin portion of the base plate between the bottom of the depressed portion and the bottom of the base plate and the element having the lower coelcient of expansion at all times and substantially throughout its length being spaced from direct thermal contact with the said element having the higher coefcient of expansion and from direct thermal contact with the said base plate, an extended electric heating element in direct heat-transferring engagement with the base -plate, means for screening the heat responsive device from direct heating elect of the heating element, the heat capacity of said element being greater than any possible working absorption of l having a depressed portion therein, the thickness between the bottom of the depressed portion and the bottom of the base plate being relatively small, a temperature responsive device comprising metallic elements having different coeillcients of expansion mounted in the depressed portion, the element having the higher coefiicient of expansion engaging the bottom of the depressed portion substantially throughout its length and having upwardly turned edges to give rigidity to the said element and insure contact with the said bottom whereby said element is'at all times and throughout its entire length directly responsive to the temperature of the thin portion oi' the base plate, anelectric heatingllelement in heattransferring engagement with the base plate, and means for causing the temperature responsive device to control `the energization of the heating element in accordance with the demands of the base plate as evidenced by the temperature change at the thin portion thereof.

5. An automatic electric iron having abase plate of relatively high thermal capacity constituting a heat storage element, said base plate 'having a depressed portion therein, the thickness between the bottom of the depressed portion and the bottbm of the base plate being relatively small, a temperature responsive device comprising metallic elements having diii'erent coefficients or expansion mounted in the depressed rigidity to the said element and insure contact 1 with the said bottom whereby said element is at all times and` throughout its entire length directly responsive to the temperature of the thin portion of the base plate, an electric heating element in heat-transferring engagement with the base plate, and means for causing the temperature responsive device to control the energiza- -tion oi' the heating element in accordance with the demands ofthe base plate as evidenced by the temperature change at the thin portion thereof.

6. An automatic electric iron comprising, in combination, a thick base plate constituting a heat storage element, shell means above and attached to said base plate, an electric heating element in heat transfer relationship with said base plate, means for ysupplying electric current to said heating element, said base plate having a depressed portion therein establishing a thin portion in the said base plate between the bottom of the depressed portion and the bottom oi the base plate, and thermostatic means in said depressed portion adapted to regulate the flow of electricity from said supply means to said heating element in accordance with the demands of the base plate as evidenced by the ytemperature change at the thin portion of the base plate, said thermostatic means comprising two metallic -elements with different coeflicients of expansion and having their ends secured together and the element having the higher coeicient of expansion being free upon expansion and contraction to move with respect to the said base plate and engaging the bottom of the depressed portion substantially throughout its length.

7. An automatic electric iron having a base plate of relatively high thermal capacity constituting -a heat storage element, said base plate having a depressed portion therein, the thickness between the bottom of the depressed portion and the bottom o1' the base plate being relatively small, a temperature responsive device comprising metallic elements having diierent coeflicients of'expansion mounted in the depressed portion, the element having the higher coeilicient of expansion engaging the bottom of the depressed portion substantially throughout its length'and having upwardly disposed means to give rigidity to the said element and insure contact' with thesaid bottom whereby said element is at all times and throughout its entire length directly responsive to the temperature of the thin portion of the base plate, an electric heating element in heat-transferring engagement with the base plate, and means for causing the by the temperature change at the thin portion thereof.

' WILLIAM A. BARNES. 

